A senior RUC intelligence officer who crossed the border to meet with confidential sources said he trusted a controversial former Garda detective sergeant with his life.

The now retired Assistant Chief Constable, identified as Witness 27, travelled south to meet the source, and introduced him to ex-detective sergeant Owen Corrigan, the Smithwick tribunal heard.

On one occasion as the two men travelled to meet the source, Corrigan spotted cars belonging to local republicans and warned Witness 27 they had to get away from the area quickly. The witness said Corrigan saved his life by his actions.

The last meeting took place less than a month before the IRA ambush in which RUC chief superintendent Harry Breen and superintendent Bob Buchanan perished on their way back from a meeting in Dundalk Garda station.

The tribunal is looking at claims that a Garda 'mole' leaked information to the IRA about the visit. Mr Corrigan has described allegations that he was behind any leak as "a monstrous lie".